Foley Janet, Branston Tammy, Woods Leslie, Clifford Deana
Department of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, California 95616, USA.
J Parasitol. 2013 Aug;99(4):595-8. doi: 10.1645/12-4.1. Epub 2013 Mar 4.
The entire range of the critically endangered Amargosa vole (Microtus californicus scirpensis) consists of less than 20 km(2) of riparian habitat in the Amargosa River drainage of the Mojave Desert in southern California. In September 2010, deformities on ears and chiggers on the ears and genitalia were detected, with some individuals so severely affected that they were missing ear pinnae altogether. Follow-up trapping was performed to document the presence of mites and mite-associated disease, and molecular characterization was performed on the mites. Of 151 Amargosa voles sampled from February to April of 2011, 60 (39.7%) voles had hard orange mites adhered to some part of their bodies, on ears of 46 (76.7%), on genitalia of 11 (18.3%), and near mammary tissue of 13 (21.7%) voles. Gross lesions were not detected on genitalia, but 47% of all individuals examined showed pinnal lesions and deformities, which included alopecia, swelling, marginal necrosis, and ulceration, as well as scarring, scabbing, and loss of pinna mass covering 25-100% of the pinnae. Biopsies revealed parakeratotic hyperkeratosis and acanthosis with diffuse neutrophilic exocytosis and dense necrotic granulocytes in the epidermis and superficial dermis associated with focal erosion and ulceration. In the underlying dermis, there were dense pleocellular inflammatory cell infiltrates composed primarily of necrotic granulocytes and multifocal hemorrhage. In some samples, mite mouthparts could be seen penetrating the superficial epidermis associated with focal necrosis, and mite fragments were found on the surface epidermis and within hair follicles. Microscopic examination of the mites documented that they were a larval trombiculid in the genus Neotrombicula with anatomical features that most closely resemble Neotrombicula microti, based on scutal shape, setation, and texture. PCR of 2 mite pools (each consisting of 3 mites from an individual animal) amplified 331 bp amplicons, which had 92-97% homology with the 18S rRNA gene of Leptotrombidium deliense, although coverage of Trombiculidae in GenBank is sparse. The severity and prevalence of lesions due to this chigger were atypical and distinct. Severe clinical trombiculiasis in this endangered species could negatively impact individual health and fitness.
极度濒危的阿马戈萨田鼠（Microtus californicus scirpensis）的整个分布范围，仅局限于加利福尼亚州南部莫哈韦沙漠阿马戈萨河排水系统中不到20平方千米的河岸栖息地。2010年9月，人们发现这些田鼠耳朵出现畸形，耳朵和生殖器上有恙螨，部分个体受影响严重，耳廓完全缺失。随后进行了诱捕，以记录螨虫及与螨虫相关疾病的存在情况，并对螨虫进行分子特征分析。在2011年2月至4月间采集的151只阿马戈萨田鼠中，60只（39.7%）田鼠身体的某些部位附着有坚硬的橙色螨虫，其中46只（76.7%）在耳朵上，11只（18.3%）在生殖器上，13只（21.7%）在乳腺组织附近。生殖器上未发现明显病变，但在所有检查的个体中，47%出现了耳廓病变和畸形，包括脱毛、肿胀、边缘坏死和溃疡，以及结痂、结疤和耳廓质量损失，损失范围覆盖耳廓的25%至100%。活检显示，表皮和浅表真皮出现不全角化性角化过度和棘皮症，伴有弥漫性嗜中性粒细胞外渗和密集的坏死性粒细胞，同时伴有局灶性糜烂和溃疡。在深层真皮中，有密集的多细胞炎性细胞浸润，主要由坏死性粒细胞和多灶性出血组成。在一些样本中，可以看到螨虫口器穿透浅表表皮并伴有局灶性坏死，在表皮表面和毛囊内发现了螨虫碎片。对螨虫的显微镜检查表明，它们是新恙螨属的幼虫恙螨，根据盾板形状、刚毛和质地，其解剖特征与微小新恙螨最为相似。对2组螨虫样本（每组由来自一只动物的3只螨虫组成）进行PCR扩增，得到331 bp的扩增子，与地里纤恙螨的18S rRNA基因有92%至97%的同源性，尽管恙螨科在GenBank中的序列覆盖较少。这种恙螨导致的病变严重程度和发生率具有非典型性且十分独特。这种濒危物种中严重的临床恙螨病可能会对个体健康和生存能力产生负面影响。
